Egyptian security forces have killed 12 Mexicans and Egyptians and injured another 10 "by accident" in an attack after mistaking a tourist convoy for militants they were pursuing in the country's western desert, the ministry of interior said.

Key points

Interior ministry says joint police and armed forces had been chasing jihadists in the Western Desert

It says the victims had been in an area that was off limits to foreigners

Mexican president Enrique Pena Nieto said two Mexicans were killed, though Egyptian security and judicial sources later said that eight Mexicans and four Egyptians were killed, and eight Mexicans and two Egyptians were wounded.

The tourist group of 22 had parked their four 4WD vehicles off road for a barbecue near the Bahariya oasis, a tourist site in the western desert, when army aircraft suddenly began shelling them from above, security sources said.

As members of the tourist convoy tried to flee, additional security forces on the ground fired on them.

"Unfortunately we have confirmed that two [Mexicans] lost their lives and six more were wounded," said Mr Pena Nieto, condemning the incident.

"Mexico has demanded the Egyptian government conducts a swift, exhaustive investigation."

They each said separately they had been bombarded from the air by a plane and helicopters.

Ruiz Massieu, Mexico's ambassador to Egypt

Mr Pena Nieto said he had been assured Egypt's prime minister would personally spearhead a probe.

Six Mexicans who survived the incident told Mexico's ambassador to Egypt they had been bombed by helicopters and an aircraft while they stopped for a break in the desert.

"They each said separately they had been bombarded from the air by a plane and helicopters," Ruiz Massieu said.

She gave no details about the identities of the tourists, other than that they had arrived in Egypt on September 11.

The Reuters news agency, however, spoke to Araceli Rangel Davalos, whose nephew Rafael Bejarano was killed and sister Marisela was wounded in the attack.

She said she knew the group's guide, an Egyptology expert whom she identified as Nabil Altawami, well. She had not yet spoken to her sister.

"I have travelled with the guide around nine times, and he never exposed us to any danger. He protected us," she said by telephone.

A joint force from the Egyptian police and military had been chasing militants in the country's vast western desert when it came across the tourist convoy, which it mistook for the militants it was pursuing, the interior ministry said in a statement.

Egypt's army spokesperson declined to comment and said only to refer to the interior ministry statement.

On Sunday (local time), Islamic State released a statement carried by its supporters on Twitter saying it had repelled an attack by the Egyptian military in the western desert.

Security officials say militants operating from Libya to the west of Egypt have been trying to forge ties with Islamists in the Sinai on the east side of the country.

The vehicles used by the tourist convoy closely resembled those of the militants the joint force had been pursuing, security sources said.

Egyptian authorities attempt to defend, Mexico protests

Mexico condemns these deeds against our citizens and has demanded an exhaustive investigation of what has occurred

Mexican president Enrique Pena Nieto

Egyptian tourism federation chairman Elhamy Elzayat offered the explanation that "the area is a restricted area, and the company made a mistake by taking the tourists to that area without a permit. They must obtain a permit before going there".

Officials at the company that organised the tour were not immediately available for comment.

"Mexico condemns these deeds against our citizens and has demanded an exhaustive investigation of what has occurred," Mexican president Enrique Pena Nieto said on his Twitter account.

Despite the apparent danger of the area, there are no warning signs along the desert path, and the attack occurred despite an official police representative accompanying the tourist convoy, said tour guide syndicate leader Hassan al-Nahla.

"Because of this negligence and lack of coordination between the ministry of tourism and ministry of interior, Egypt ... will pay the price when this affects tourism," he added.

While the Islamist insurgency has been largely based in the Sinai Peninsula, attacks have taken place in Cairo and other cities.